Why does my phone keep adding an extra 1 to numbers that text me?

Okay, so starting last night when a friend would text me my galaxy s5 active kept adding an extra one to numbers. So when I would receive a text the number would come in as +1-1-555-555-5555. All the texts I received had a number like that but if I tired to respond to it I would get an invalid number message back. So basically I was reading text from the weird number and having to exit and reply to the actual right number. I have no clue how to fix this.